A plasma reactor for processing a workpiece can employ an electron beam to generate plasma in a processing chamber. The electron beam source produces a high-energy, sheet electron beam, which is injected into the processing chamber. As the electron beam propagates through the processing chamber, it produces plasma for etching or other applications. Such a plasma reactor can exhibit non-uniform distribution of processing results (e.g., distribution of etch rate across the surface of a workpiece) due to non-uniform distribution of electron density and/or kinetic energy within the electron beam. Such non-uniformities can be distributed in a direction transverse to the beam propagation direction.